﻿<p>The schema <em>IfcProfileResource</em>
defines the two dimensional profiles or cross sections, used to define
geometric shape representations. Profile definitions are applied to:</p>
<ul>
  <li>swept surfaces</li>
  <li>swept area solids</li>
  <li>sectioned spines</li>
</ul>
<blockquote class="note">
NOTE&nbsp; Profile
definitions are not subtypes of geometric representation item and can
not be used directly to geometrically represent an object.
</blockquote>
<p>Profiles can be used to either
define a curve or an area. In case of a curve, only the boundary is in
the domain of the profile definition, in case of an area the boundary
and the inside is in the domain of the profile definition. A curve can
be used for</p>
<ul>
  <li>swept surfaces</li>
  <li>sectioned spines</li>
</ul>
<p>and an area can be used for</p>
<ul>
  <li>swept area solids</li>
  <li>sectioned spines</li>
</ul>
<blockquote class="note">
NOTE&nbsp; The use of
profile definitions is the preferred way to define prismatic shapes to
represent products.
</blockquote>
<p>The profile definition (<em>IfcProfileDef</em>)
can be instantiated by the various subtypes. There are four different
groups of profile definitions:</p>
<ul>
  <li>parametrically defined
profiles, these profiles are defined by a 2D position coordinate system
and dimension parameters to generate a 2D form.</li>
  <li>explicitly defined profiles,
these profiles are defined by a (single or multiple) 2D curve(s) defined
in the parent coordinate system.</li>
  <li>derived profiles, these
profiles are created by a Cartesian transformation of a parent profile.</li>
  <li>composite profiles, these
profiles are compositions of other profiles</li>
</ul>
<p>When used as the curve or area
to be swept into a surface or solid, the 2D coordinate system of the
profile is mapped into the xy plane of the 3D coordinate system of the
swept surface (subtypes of <em>IfcSweptSurface</em>),
the swept area solid (subtypes of <em>IfcSweptAreaSolid</em>),
or the sectioned spine (<em>IfcSectionedSpine</em>).
The extrusion direction is along the z axis of the 3D coordinate system
(or an extrusion vector being not perpendicular to the z axis, or a
rotation that has a tangent into the z axis at the point of origin).</p>

<p>The use of
coordinate axes in IFC is not identical with the general convention for the use of coordinate axes in structural analysis. The following conversion should be used, as shown in Figure 307:</p>

<table>
  <tbody>
    <tr valign="top">
      <table cellspacing="4">
        <tbody>
          <tr>
            <td><u>IFC axes convention</u></td>
            <td><u>Structural analysis axes convention</u></td>
          </tr>
          <tr>
            <td>+X</td>
            <td>-Y</td>
          </tr>
          <tr>
            <td>+Y</td>
            <td>-Z</td>
          </tr>
          <tr>
            <td>+Z</td>
            <td>+X</td>
          </tr>
        </tbody>
      </table>
      </td>
    </tr>
  </tbody>
</table>

<table>
<tr><td><img src="../../figures/ifcprofileresource-coordinatesystem.gif" alt="coordinates in IFC and structural" border="0"
 height="300" width="400"></td></tr>
<tr><td><p class="figure">Figure 408 &mdash; Profile coordinate system</p></td></tr>
</table>

<blockquote class="history">
HISTORY&nbsp; New schema in IFC2x, definitions had been part of the <em>IfcGeometryResource</em>
in earlier IFC Releases.  <em>IfcProfilePropertyResource</em> schema merged
into <em>IfcProfileResource</em> in IFC4.
</blockquote>